The invention relates to a process for producing pig iron or liquid primary steel products in a blast furnace, CO2 being substantially removed from at least a partial stream of a top gas emerging from a reduction shaft furnace, and this partial stream if appropriate being heated and being introduced into the blast furnace as reduction gas, and to a plant for carrying out this process.
A process of this type is known from DE 4421673A1. In this process, the top gas, after CO2 has been removed, is mixed with hot nitrogen or with hot nitrogen-containing and argon-containing gas and is thus heated to over 800° C. In the process, heated top gas from which CO2 has been substantially removed is fed to the blast furnace via a hot-air distribution pipe. The heating of the top gas must be carried out extremely quickly while avoiding reaction of the CO gas in accordance with the Boudouard equilibrium and avoiding reaction of the H2 gas according to the heterogeneous water gas reaction, resulting in a considerable outlay on process and plant technology.
U.S. Pat. No. 3,954,444 A1 relates to a process for the direct reduction of iron ores. In this process, a portion of the reducing gas is removed from a shaft furnace, is treated and is then fed back to the shaft furnace. In this case, in a particular embodiment the reducing gas can also be introduced into a blast furnace as reducing agent. In this process too, the regeneration of the gas is laborious and involves a high outlay on process and plant technology.
With a view to the prior art, it is an object of the invention to develop a process and a plant for carrying out this process which, compared to the prior art, results in an improved energy balance and improved process management.